This invention is directed to new and useful improvements in sedimentation apparatus having rotatable sediment rake arm mechanisms and in particular to rake lifting means for such rake arm mechanisms.
In sedimentation apparatus which comprise circular or square settling tanks it is well known to provide at least one pair of rotating rake arms driven by rotatable drive means which are mounted on a fixed column at the center of the tank. The rake arms are provided with raking blades which are adapted to engage and move sediment or sludge collected on the tank bottom to a central discharge sump. It is common practice to provide means for raising the rake arms should an overload condition exist such as when unusually deep sludge deposits or other obstructions are encountered by the rake blades. The lifting mechanisms are adapted to automatically raise some or all of the rotating rake arms until the overload condition is abated.
Prior art rake arm lifting mechanisms are typified by the the devices disclosed in the following U.S. Pat. Nos.:
867,958 PA1 1,734,044 PA1 2,064,151 PA1 2,122,383 PA1 2,437,761 PA1 2,557,316 PA1 2,650,707 PA1 3,200,956 PA1 3,549,017
Although the rake lifting mechanisms of these prior disclosures have proven effective for their intended purposes, various problems are encountered in that they include relatively complex structures for raising the rake arm or alternatively do not assure that the rake arms are moved upwardly in manner whereby the inner ends of the rake arms are raised an equidistance from the tank bottom as the outer ends. In the known mechanisms complex hinge arrangements are required resulting in increased torque requirements for lifting of the main drive mechanism with the rake arms or the rake arms alone to accomplish these objectives.
It is an object of the present invention to provide a novel rake lifting mechanism for the rotatable rake arms of a sedimentation settling tank.
Another object is to provide a rake arm lifting mechanism comprised of a novel linkage arrangement between the rake arms and the drive mechanism therefor for raising the rake arms vertically an equidistance from the tank bottom.
A further object is to provide a novel rake lifting mechanism comprised of a relatively few and non-complex parts which require only a minimum operating area for lifting the rake arms a given distance and at the same time reducing torque requirements.